In recent years, thermal transfer systems have been developed to obtain prints from pictures which, for example, have been generated electronically from a color video camera. According to one way of obtaining such prints, an electronically generated picture is first subjected to color separation by color filters to obtain, for example, three color-separated images. The respective color-separated images are then converted into three separate electrical signals. These three electrical signals are then operated on to produce representative cyan, magenta, and yellow electrical signals which are transmitted to a thermal printer. To obtain the print, a cyan, magenta, or yellow dye-donor element or sheet is placed face-to-face with a dye receiving element or sheet. The dye-donor element and the dye receiving element are then inserted between a thermal printing head and a platen roller or drum. A linear thermal printing head is used to apply selective heat from the back of the dye donor sheet to cause the dye from the dye donor element of the printing media to be released to reproduce the image portion of one color. The process is then repeated for the other two colors using any known accurate registration technique for ensuring that the corresponding pixels of each color image are properly registered to produce a sharp image print.
Another way to thermally obtain a print using the electronic signals described above is to use one or more lasers instead of a thermal printing head. In such a laser printing system, the dye-donor sheet includes a material which strongly absorbs light at the wavelength of the laser being used. When the dye-donor sheet is irradiated, the absorbing material converts light energy to thermal energy and transfers the heat to the dye in the immediate vicinity, thereby heating the dye to its vaporization temperature for transfer to the dye receiver sheet. The light absorbing material is generally present in a layer beneath the dye and/or admixed with the dye. The laser beam is modulated by the electrical signals which are representative of the shape and color of the original image so that each dye color is heated to cause volitization only in those areas where its presence is required on the dye receiver member to reconstruct the color of the original image. Various printing media have been developed for use with laser printers.
U.S. Pat. No. 4,816,367 (H. Sakojiri et al.), issued on Mar. 28, 1989, discloses a multicolor imaging material comprising a substrate, and a capsule layer made up of (a) a plurality of heat-meltable microcapsules including separate color formers for three primary colors, and (b) a developer layer. FIG. 7 of this patent shows a laser printing arrangement comprising three lasers that generate separate light beams of different wavelengths and beam combining means. This laser printing arrangement merely provides a simple tool for combining light beams of three different wavelengths for projection onto the multicolor imaging material. More particularly, the three laser light beams having separate wavelengths are applied to the multicolor imaging material in accordance with electrical laser modulating input signals corresponding to the three primary colors of an original image. In response to the laser light beams, the heat-meltable microcapsules for the individual colors independently generate heat causing the heat-meltable substance to be selectively melted or not melted and produce correspondingly colored pixels of the original image on the imaging material. Another example of a similar type one-microcapsule layer color imaging materials is given in U.S. Pat. No. 5,053,309 (F. Sanders et al.), issued on Oct. 1, 1991.
U.S. Pat. No. 5,122,432 (W. Hammann IV et al.), issued on Jun. 16, 1992, discloses a photosensitive printing media including a support, and a plurality of microcapsule sets and a color correction dye associated with the sets of microcapsules mounted in layers on the support. In one embodiment, a first layer including microcapsules of a first color dye surrounded by, or adjacent to, a layer of a color correction dye which absorbs light within a spectral sensitivity range of the first color microcapsules is formed on the support, and a second layer including microcapsules of one or more second colors surrounded by, or adjacent to, a layer of an appropriate color correction dye is formed on the first layer. In a second embodiment, a first layer comprising a first set of microcapsules that are sensitive to red light and a layer of cyan color correction dye is formed on the support, a second layer comprising a second set of microcapsules that are sensitive to green light and a layer of an magenta color correction dye is formed on the first layer, and a third layer comprising a third set of microcapsules that are sensitive to blue light and a layer of a yellow color correction dye are formed on the second layer. The color correction dyes each absorb at least one of the red, green, or blue light.
Referring now to FIG. 1, there is shown a printing media 10 which is disclosed in U.S. patent application Ser. No. 992,235, now U.S. Pat. No. 5,234,890 (assigned to the present assignee), filed on Dec. 17, 1992. The printing media 10 comprises a multicolor, multilayer dye donor element 12 for laser induced thermal dye transfer to a receiver member 14. The dye donor element 12 comprises a support 16 having formed thereon three layers of microcapsules (beads) 17, 18, and 19 on top of each other with each layer containing a different colored dye. More particularly, each microcapsule dye layer comprises solid, homogeneous beads which contain an image dye, a binder, and a laser light-absorbing material which is sensitized to a different wavelength of light. It is to be understood that the printing media 10 need not always contain three dye layers, and can comprise any number of two or more dye layers formed on the support 16 for laser induced dye transfer using light beams of different wavelengths.
It is to be understood that in the various printing media known in the prior art, the microcapsules or beads containing the dye of each of two or more colors may or may not have a same size, and/or may or may not have a same sensitivity or behavior with a particular wavelength light associated therewith. The problem is that the prior art laser printers provide arrangements which are not designed in accordance with specific parameters of a color printing media. In other words, the prior art laser printers only provide general tools for multicolor printing and do not consider or provide compensation for parameter variations of different printing media. As a result, the prior art laser printers cannot efficiently transfer two or more different dyes from a dye donor member to a dye receiving member using different wavelength laser light beams.
Therefore, it is desirable to provide laser printers which emit light beams of different wavelengths that are optically processed and scanned to provide selective sized focused beams at a printing media being used and thereby efficiently match the separate color parameters of the printing media.